Another convention sometimes used is that, since 12 noon is by definition neither ante meridiem (before noon) nor post meridiem (after noon), then 12am refers to midnight at the start of the specified day (00:00) and 12pm to midnight at the end of that day (24:00).
The American Heritage Dictionary of the English Language states "By convention, 12 AM denotes midnight and 12 PM denotes noon. Because of the potential for confusion, it is advisable to use 12 noon and 12 midnight."
Re: 12 am = midnight or noon? Midnight is 12:00 pm. It is also 00:00 am. This is because it represents both the beginning and the ending of a set of numbers that runs from 00:00 to 12:00.
The universal convention is that 12:00 AM signifies midnight, and every moment afterward is also 'AM' until the precise moment of 12:00 PM which is midday.
12am is the exact moment the 12th hour of the morning finishes (am), and similarly for pm. Therefor 12am is midday and pm would start straight after.
There are no standards established for the meaning of 12am and 12pm. It is often said that 12am Monday is midnight on Monday morning and 12pm is midday. This puts all the times beginning with 12 and ending with am in the same one-hour block, similarly with those ending with pm.
The answer is very simple 12:30 am is morning and 12:30 pm is in the afternoon.
Midnight and midday
Some will say midnight is 12am, and therefore that midday (or noon) is 12pm.
5 AM is early in the morning and 5 PM is late in the afternoon; 1 AM is one hour after midnight, and 11 PM is one hour before midnight. Ante meridiem is generally referred to as AM, am, a.m., or A.M whereas PM, pm, p.m., or P.M. are typically abbreviated post meridiem.
The word noon is derived from Latin nona hora, the ninth canonical hour of the day, in reference to the Western Christian liturgical term none, one of the seven fixed prayer times in traditional Christian denominations.
The term you are probably looking for is the small hours. Collins defines this term as "the early hours of the morning, after midnight and before dawn."
For example, “Good morning” is generally used from 5:00 a.m. to 12:00 p.m. whereas “Good afternoon” time is from 12:00 p.m. to 6:00 p.m. “Good evening” is often used after 6 p.m. or when the sun goes down. Keep in mind that “Goodnight” is not a salutation. In formal communication, it is used to say goodbye.
12:00AM is in the next day/at the start of the day. The previous day ended at the end of the last second of the previous day which was 11:59:59PM. The next second is the first second of the next day: 12:00:00AM to 12:00:01AM. (Think of it as/Often it is referred to as 00:00:01.)
As the dividing point between one day and another, midnight defies easy classification as either part of the preceding day or of the following day. Though there is no global unanimity on the issue, most often midnight is considered the start of a new day and is associated with the hour 00:00.
Going to bed after midnight “can lead to chronic exhaustion and fatigue and even thyroid problems and burnout,” Ramlakhan says. According to Ramlakhan's research and experience working in the field of sleep science, many people who go to bed later tend to oversleep the next day.
"Our body and brain tend to repair better too before midnight, so much so that those some studies (one of which examined 400,000 people over the space of 6.5 years) have even suggested those who get to bed before midnight tend to live longer than those who don't."
When most people say 12pm, typically they're talking about the middle of the day: 12 noon. When they say 12am, they normally mean 12 midnight.
The meaning of AM and PM is 'Ante Meridiem' and 'Post Meridiem', which means before noon or midday. We associate P.M. with the afternoon and evening. P.M. is an abbreviated term for 'Post Meridiem,' which implies afternoon or after midday. In a 12-hour clock, these are used as time indications centered around noon.
The “M” represents “Meridian” which means Latin for “Noon.” “A” represents “Ante”, which means before in Latin, while “P” represents “Post”, which means after in Latin. 12 Noon is neither AM, Ante Meridian (before noon) nor Post Meridian (after noon).
The reason a new day starts at 12:00 goes back to ancient Egypt when the day was measured using sundials. The shadow on the face of a sundial tells the time, and the shadow depends on where the sun is in the sky. "When the sun is highest overhead and the shadow goes straight up to the top of the sundial, that's noon.
Therefore, if it's before 11:59 PM, 12:00 AM would be considered tomorrow. If it is 12:00 AM or after, it's considered today.
As standard 12:00 AM is taken as the start of the day. Time of the day is divided in two halves (24hour= 12 hours before midday + 12 hours after midday) so the 11 AM is 11th hour before midday as clock strikes 12 again it changes to PM (after midday) so it's 12 PM after 11 AM and 12 AM after 11 PM.
As standard 12:00 AM is taken as the start of the day. Time of the day is divided in two halves (24hour= 12 hours before midday + 12 hours after midday) so the 11 AM is 11th hour before midday as clock strikes 12 again it changes to PM (after midday) so it's 12 PM after 11 AM and 12 AM after 11 PM.